It is known that various water-soluble phthalocyanine and naphthalocyanine compounds, in particular those having certain metals as the central atom, have a photosensitizing action and can therefore be used as photo-bleaching agents or anti-microbial active compounds.
Phthalocyanines and naphthalocyanines especially when combined with a suitable metal can undergo a series of photochemical reactions in conjunction with molecular oxygen to produce molecules of "singlet oxygen". The excited "singlet oxygen", formed in these photosensitizing reactions, is an oxidative species capable of reacting with stains to chemically bleach them to a colorless and usually water-soluble state, thereby resulting in what is called photochemical bleaching.
There are many examples of photobleaches comprising phthalocyanines and naphthalocyanines, the most common being the zinc and aluminum phthalocyanines. In the literature the term "photosensitizer" is often used instead of "photoactivator" and may therefore be considered as standing equally well for the latter term used throughout this specification
The prior art teaches phthalocyanine and naphthalocyanine compounds having the general structure ##STR1## where Me is a transition or non-transition metal, (Sens.) is a phthalocyanine or naphthalocyanine ring which, when combined with a suitable Me unit, is capable of undergoing photosensitization of oxygen molecules, R units are substituent groups which are bonded to the photosensitization ring units (Sens.) to enhance the solubility or photochemical properties of the molecule, and Y units are substituents associated with the metal atom, for example, anions to provide electronic neutrality. The selection of a particular substituent R unit for substitution into the molecule has been the focus of many years of research and these units are typically chosen by the formulator to impart into the target molecule the desired level of water solubility without affecting the degree of photosensitizing properties.
A major limitation to the use of phthalocyanine and naphthalocyanine compounds for fabric photobleaching is the fact that these molecules have a Q-band absorption maxima (.lambda..sub.max) in the range of visible light that is. Therefore they are highly colored materials. Phthalocyanines have Q-band absorption in the range of 600-700 nanometers, while naphthalocyanines have Q-band absorption in the 700-800 nanometer range. This is not surprising given the fact that these molecules are structurally similar to dyestuffs.
A second limitation arises from the fact that the parent phthalocyanine and naphthalocyanine compounds when combined with a transition or non-transition metal are not inherently water soluble. This fact is especially true in the case of naphthalocyanines. It has therefore been the task of phthalocyanine and naphthalocyanine photobleach formulators to select for R units moieties that are polar or hydrophilic, then attach these moieties to the (Sens.) unit in an attempt to increase the molecule's water solubility without adversely affecting the photochemical properties of the ring system.
A further task for the formulators of phthalocyanines and naphthalocyanines has been the need to modify the properties of the (Sens.) unit of the molecule to increase the "photobleaching capacity" (photophysics) of the molecule, in other words, to increase the quantum efficiency. Again, selection of suitable R units to accomplish this task must not in turn adversely affect the water solubility. While balancing water solubility and enhanced photophysics, the formulator must insure that the structural modifications do no shift the .lambda..sub.max of the Q-band to a wavelength that is now in the visible region. Maintaining the Q-band .lambda..sub.max to a wavelength above 660 nm, while not having the more desirable "low hue" properties of materials exhibiting a Q-band .lambda..sub.max of 700 nm or greater, it provides a molecule with photobleaching properties acceptable to consumers.
It is well known to formulators skilled in the art that an R unit which may produce a desired increase in one of these three properties may cause an equally large decrease in one or both of the other desirable properties. For example, a change which increases solubility may reduce the quantum efficiency of the molecule and thereby render the final molecule without sufficient photobleaching properties. Exacerbating this problem further is another factor; choice of a suitable Y group. Many phthalocyanine and naphthalocyanines comprise a metal or non-metal atom that is hypervalent to the chelate ring system. Satisfying the valency requirement of these atoms or providing for the electronic neutrality of the molecule may cause the delicate balance of properties, once achieved, to collapse.
Surprisingly, it has been found that the compounds of the present invention allow the formulators to modify the levels of solubility, photoefficiency, Q-band wavelength maxima and the electronic requirements of the central silicon atom separately without adversely affecting the other parameters of the molecule. This ability to delineate and selectively modify the key structural elements contributing to the target properties of the molecule allows the formulator to proceed without having to rely upon a "hit and miss" stratagem.
One key to this ability to control the molecular properties is found when contrasting the structure of known photobleaches comprising phthalocyanines and naphthalocyanines with those of the present invention. The examples of photobleaches previously described in the art are generally flat molecules due to their planar ring structure. This inherently leads to molecular stacking, layering and other forms of aggregation which tend to clump the molecules together. A photobleach molecule which is overlaid by other photobleach molecules will tend to quench each other thereby effectively stopping the generation of singlet oxygen.
The organosilicon photosensitizing compounds of the present invention comprise axial substituents that act to break up this ordering effect, hence providing an efficiently formed mono-layer of photosensitizers evenly applied to a given substrate. Because each molecule of this mono-layer can now contribute to bleaching there is better cost efficiency to the formulator.
It has been surprisingly found that because of the separating out of physical properties into "molecular sectors", e.g. R groups for solubility, new uses for the compounds of the present invention have been realized. Adducts which provide unique solubility profiles, but which detract from the photophysics, were once excluded from use in photobleaches. However, the inclusion of these moieties into the photobleaches of the present invention results in the ability to formulate photobleaches for use in non-classical applications, for example dry cleaning applications. Solvent based or low aqueous solutions of the present invention are now obtainable for the very reason that control over solubility is manifest in the choice of the axial R substitutions.
The proper selection of axial R units attached to the compounds of the present invention allow the formulator to balance the changes in photoefficiency of the desired compound with the water solubility of the parent material. In addition, these axial R unit modifications provide the formulator with the ability to balance solubility, Q-band .lambda..sub.max, and quantum efficiency of the (Sens.) unit.
It is an object of the present invention to provide "substantive" and "non-substantive" organosilicon photosensitizers. The terms "substantive" and "non-substantive", as used in the present specification and as further defined hereinafter, describe the propensity of a compound to elicit a surface affinity or, in the alternative, the lack of a surface affinity, in other words a "substantive" organosilicon photosensitizer will be attracted to a surface and a "non-substantive" organosilicon photosensitizer will repel a surface.
It is a further object of the present invention to provide substantive and non-substantive photobleaching laundry compositions for natural, synthetic or blended fabrics.
It is a further object of the present invention to provide photobleaching compositions that comprise non-aqueous and low aqueous carriers, that is, photobleaching compositions having carriers wherein water constitutes less than half of the carrier liquid.
It is a further object of the present invention to provide photobleaching compositions and cleaning compositions comprising substantive materials for non-porous hard surfaces, inter alia, Formica.RTM., ceramic tile, glass, or for porous hard surfaces such as concrete or wood.
An object of the present invention is to provide a method for bleaching fabric with laundry compositions comprising organosilicon photosensitizing compounds of the present invention.
An object of the present invention is to provide a method for cleaning hard surfaces with compositions comprising organosilicon photosensitizing compounds of the present invention.
An object of the present invention is to provide for low hue organosilicon photosensitizing compounds having a Q-band maximum absorption wavelength of at least 660 nanometers.